1. Field of the Invention
The present invention relates to a controller of a disk array apparatus configured by a plurality of magnetic disk drives used for storing data respectively.
2. Description of the Related Art
[Patent Document 1]
JP-A No. 256003/2001
Large-scale corporations such as banks, securities firms, telephone companies are now trying to reduce the costs of the operation, maintenance, and management of their computer systems and storage systems by integrating those computers and storages in a data center respectively while they have been distributed to some places so far.
In order to meet such the demands, large high-end disk array controllers are beginning to support the channel interfaces with more than one hundred host computers (connectivity) and the storages, each having a large capacity of more than several hundreds of terabytes.
On the other hand, along with the expectation that the storage area network (SAN) will spread more in the near future, small-scale disk array controllers are also coming to be required of the same enhanced high reliability as that of the large high-end disk array controllers.
As a result, each of the disk array controllers as described above has now been configured with scalability to cope with any of small-scale and large-scale configurations with the same enhanced highly reliable architecture. And, one of the methods for enabling such the disk array controller is to integrate a plurality of disk array controllers so as to operate them as one system.
FIG. 2 shows an outline of the disk array controller disclosed by JP-A No. 256003/2001 as an example of the conventional techniques for those disk array controllers. According to this conventional technique, the disk array controller comprises a plurality of disk array control units, each including a plurality of channel IF units 11 used for the data transfer between a plurality of host computers 50 and the plurality of disk array control units 1; a plurality of disk IF units 12 used for the data transfer between a plurality of magnetic disk drives 5 and the plurality of disk array control units 2; a plurality of cache memory units 14 for storing data read/to be written from/in the plurality of magnetic disk drives 5 temporarily; and a plurality of shared memory units 13 for storing control information related to the disk array control units 1 (ex., information related to the controlling of the data transfer between the channel IF units 11/disk IF units 12 and the cache memory units 14, and management information of the data to be stored in the magnetic disk drives 5). The shared memory units 13 and the cache memory units 14 can be accessed from every channel IF unit 11 and every disk IF unit 12 over the plurality of disk array control units 1. In this configuration of the disk array controller, inter-connection networks 10 and 20 are used for the connection between the channel IF units 11/disk IF units 12 and the shared memory units 13, as well as between the channel IF units 11/disk IF units 12 and the cache memory units 14 over the plurality of disk array control units 1.
FIG. 3 shows a detailed internal block diagram of a conventional disk array control unit (DKC) 1. Each disk array control unit 1 includes a plurality of SM-SWs (shared memory switches) 110, and a plurality of SM paths between units 141, through which the units 141 are connected to the inter-connection network 10. And, each disk array control unit 1 includes a plurality of CM-SWs (cache memory switches) 111, as well as a plurality of CM paths between units 142, through which the units 142 are connected to the inter-connection network 20.
As described above, the conventional disk array controller thus comes to be able to provide any of small to super large scale configurations with scalability, since a plurality of disk array control units are connected to each another through the inter-connection networks.
However, the conventional technique does not mention details of how to configure any of such the inter-connection networks while the technique can cope with any of small to super large scale configurations with scalability by connecting plurality of disk array control units through the inter-connection networks configured by switches. And, how to form such a scalable inter-connection network is very important to realize scalable disk array controllers, whether they are small or super-large in scale. In other words, a small-scale inter-connection network should be used when the number of the connected disk array control units is not so large while a large-scale inter-connection network should be used when the number of the connected disk array control unit is large. When an inter-connection network is to be scaled up/down, the scale-down/up should be made without service interruptions while the controller's reliability is kept. In addition, the unit module for configuring a scalable inter-connection network should be fabricated with as less hardware items as possible.
Under such circumstances, it is an object of the present invention to provide a scalable disk array control unit inter-connection network to realize scalable disk array controllers.
More concretely, it is an object of the present invention to provide a disk array control unit inter-connection network to/from which scalable disk array control units can be added/removed without service interruptions while the network reliability is kept so as to provide scalable disk array controllers.
It is another object of the present invention to provide an implementation method of a cost-scalable disk array control unit inter-connection network with less hardware items.